Chiral Organomagnesiates as Dual Reagents for Bromine–Magnesium Exchange of 2-Bromopyridine and Access to Chiral α-Substituted 2-Pyridylcarbinols

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Abstract

New chiral ligand containing butyl and dibutylmagnesiates have been prepared from a range of ligands and their reactivity studied. The reagents were generally efficient in promoting the clean bromine–magnesium exchange of 2-bromopyridine at room temperature and the subsequent reaction with aldehydes to afford α-substituted 2-pyridylcarbinols in good yields. (R,R)-TADDOLate proved to be the best ligand, leading to acceptable to good enantioselectivities. To the best of our knowledge this is the first example of an organomagnesiate-induced halogen–metal exchange followed by an enantioselective addition.

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